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The standard approach often used to reduce gear noise in automotive system is to minimize the transmission error. This is done by using stringent quality control measures in the gear manufacture, selecting desirable gear parameters, and applying profile modifications. This approach may be effective in many instances. However, there are numerous examples where the gear quality is the best that can be achieved within the manufacturing constraints, and the noise levels still exceed acceptable limits. In many cases, the system dynamics cause the gear train design to be highly sensitive to manufacturing induced transmission error. Therefore, it is advantageous to perform dynamic analysis to examine the influence of gear train dynamics and design parameters on gear noise. Proper design modifications may then be identified and applied to reduce gear noise levels.

This paper describes techniques for dynamic evaluation of complex mechanical systems, particularly construction equipment. By coupling experimental and analytical techniques, a thorough understanding of system performance can be obtained, and improved predictions of dynamic failures can be made. In particular, the ability to obtain reliable predictions of system stress and/or vibration response to adverse loading conditions is presented. It is not necessary or advisable to restrict the testing of earthmoving and agricultural equipment to static loading conditions only. Dynamic studies, using combined automatic transfer function analysis (TFA) equipment and related computer capabilities, are practical and beneficial. The object of this paper is to point out advantages of dynamic investigations and to present another tool for construction and agricultural machinery engineers in their continuing endeavor to improve their products.

The design of automotive components for low structure-borne interior noise and vibration requires the ability to reliably simulate total vehicle system response over a wide operating frequency range. This implies that the car body, its interior acoustic cavity, and critical structural components must be included in this overall dynamic model. Unfortunately, most noise and vibration problems occur in the 200-1000 Hz frequency range where existing finite element and experimental modal methods have limited applicability. This is due to the high modal density, high damping levels, and sensitivity to fine geometric detail. Moreover, it is highly doubtful that these methods will ever be practical tools for the study of the total body dynamics over the frequency range of 200-1000Hz. In this paper, a practical hybrid experimental-analytical approach is proposed in response to the need to simulate high frequencies structure-borne noise and vibration in automotive systems.

In rear wheel drive vehicles, passenger perceived tonal noise is often generated by high frequency rotational vibrations of the transmission output shaft. This rotational vibration is excited by the transmission and couples with the dynamic and inertial properties of the driveline and suspension to generate forces through the suspension attachment locations. This paper demonstrates an approach which uses experimental techniques to measure the rotational dynamics of the output shaft and noise path analysis procedures to predict the vehicle system interaction and resulting vehicle noise contribution from this path. An evaluation of three rotational data acquisition techniques, a measurement technique used to characterize a vehicle's torsional acoustic sensitivity, and an application of mobility coupling to the torsional noise path is presented.

The design of automotive components for low structure-borne interior noise and vibration is facilitated by the ability to reliably simulate total vehicle system response over a wide operating frequency range. This requires that the car body, its interior acoustic cavity, and critical chassis components must be included in the overall dynamic model. Unfortunately, most noise and vibration problems occur in the 200-1000 Hz frequency range where finite element and experimental modal methods have limited applicability. This is due to the high modal density, high damping levels, and sensitivity to fine geometric detail. A simulation method has been proposed earlier which uses component finite element models and component experimental transfer functions to predict combined system response [1]. This method has allowed for a practical approach to automotive system noise and vibration simulation.

Much attention has been devoted to the importance of vehicle dynamics relative to human response ride criteria. The present work extends this effort by providing a practical computerized design approach in which the vehicle designer selects a representative terrain input, either sinusoidal or power spectral density, to excite a vehicle model constructed by the modal Building Block method. To evaluate vehicle ride the resulting system response, accounting for human dynamic characteristics, is compared to accepted ride criteria, such as ISO spectra and absorbed power. An example involving an agricultural tractor is presented to illustrate the approach.

This paper discusses the nature of noise production of automotive transmissions and the various measures which may be taken to reduce operating noise. The measures discussed include investigation and modification of the gear-shaft system dynamics in both bending and torsion. Also discussed are determination of dynamic characteristics of the transmission housing and ways of reducing the levels of vibration of housing areas and of decreasing the radiation efficiency of those areas.